As is well known, the disposal of waste sludges obtained in the treatment of municipal and industrial waste waters has long been a problem and constitutes an ever increasing threat to the environment. Indeed, it is now apparent that governmental regulations will soon seriously limit and probably eventually totally prohibit the ocean dumping of such sludges which has long been the disposal method of economic choice for coastal areas. The only options which will then remain, given present technology, will be using the processed sludges as land fill or compost for agricultural purposes, or disposal by incineration. Due to the limited availability of suitable agricultural or fillable land adjacent large urban areas where the problem is most acute, incineration is the only viable option for the disposal of such industrial and municipal sludges in such areas.
Another problem which is becoming more serious is that of safely disposing of hazardous or noxious industrial or other wastes. Such wastes vary widely in form and chemical content and may consist of solid chemical wastes, aqueous or organic liquid solutions, single or mixed liquid solvents, slurries of solids in liquids, emulsions, and so forth. Such materials may even be corrosive or highly poisonous. Materials of these types have been disposed of in a variety of ways, as by sealing in metal or other containers and sinking the containers in deep areas of the ocean. Such materials have also been pumped into deep underground caves or abandoned mines or the like. Some of the less hazardous materials have been simply buried in the ground in suitable areas. Carefully controlled, especially designed incineration operations employing fossil fuels have also been used. When such substances are buried or pumped underground, care must be taken, of course, that they are deposited either so deeply or in such a place that any noxious materials leached out of the waste by ground water cannot find their way into streams, rivers, lakes or the ocean where fish and other aquatic life, birds, animals or even humans might be harmed. For these reasons a considerable body of technology has been developed for treating such hazardous wastes to render them less noxious and safely disposable. However, such treatments are invariably expensive and the safe disposal of such wastes represents substantial economic as well as ecological problems.
Combustible bulk solid or liquid municipal and industrial waste, such as waste paper and paper board, scrap wood or tree trimmings, municipal trash and garbage, waste oil, or solvents and a host of other materials of this type can, if clean and otherwise suitable, be used as land fill if fillable land is available. Alternatively, assuming that these materials are readily combustible they may be incinerated.
It is well known, however, that the disposal of any of the foregoing waste materials by incineration generally requires the use of an auxiliary fossil fuel. More specifically, many sludges and hazardous wastes are not autogeneously combustible and it is often necessary to employ large amounts of auxiliary fossil fuels not only initially but continuously during the incineration of such materials to achieve satisfactory combustion. The available world supply of fossil fuels is limited and the unequal geographical and political distribution of such fuels is presently causing continuing substantial increases in their cost. It is apparent, therefore, that it is becoming increasingly uneconomic to employ such fossil fuels in the disposal of industrial and municipal wastes and that there is a serious need in the art for the development of technology to minimize the need for such use.